src/bin/lttng-sessiond/tsdl-trace-class-visitor.hpp

   1 /*
   2  * Copyright (C) 2022 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-only
   5  *
   6  */
   7
   8 #ifndef LTTNG_TSDL_TRACE_CLASS_VISITOR_H
   9 #define LTTNG_TSDL_TRACE_CLASS_VISITOR_H
  10
  11 #include "trace-class.hpp"
  12 #include "stream-class.hpp"
  13 #include "event-class.hpp"
  14
  15 #include <vendor/optional.hpp>
  16
  17 #include <functional>
  18 #include <unordered_map>
  19
  20 namespace lttng {
  21 namespace sessiond {
  22 namespace tsdl {
  23
  24 using append_metadata_fragment_function = std::function<void(const std::string& fragment)>;
  25
  26 namespace details {
  27 /*
  28  * Register types to be overriden. For example, a TSDL-safe copy of a type can
  29  * be added to be overriden whenever the original type is encountered.
  30  *
  31  * Note that this class assumes no ownership of the original types. It assumes
  32  * that the original types live as long as the original trace.
  33  */
  34 class type_overrider {
  35 public:
  36         type_overrider() = default;
  37
  38         void publish(const lttng::sessiond::trace::type& original,
  39                         lttng::sessiond::trace::type::cuptr new_type_override);
  40         const lttng::sessiond::trace::type& type(
  41                         const lttng::sessiond::trace::type& original) const noexcept;
  42
  43 private:
  44         std::unordered_map<const lttng::sessiond::trace::type *, lttng::sessiond::trace::type::cuptr>
  45                         _overriden_types;
  46 };
  47 } /* namespace details. */
  48
  49 /*
  50  * TSDL-producing trace class visitor.
  51  *
  52  * An instance of this class must not be used on multiple trace class instances.
  53  * The `append_metadata` callback is automatically invoked when a coherent
  54  * fragment of TSDL is available.
  55  */
  56 class trace_class_visitor : public lttng::sessiond::trace::trace_class_visitor {
  57 public:
  58         trace_class_visitor(const lttng::sessiond::trace::abi& trace_abi,
  59                         append_metadata_fragment_function append_metadata);
  60
  61         virtual void visit(const lttng::sessiond::trace::trace_class& trace_class) override final;
  62         virtual void visit(const lttng::sessiond::trace::clock_class& clock_class) override final;
  63         virtual void visit(const lttng::sessiond::trace::stream_class& stream_class) override final;
  64         virtual void visit(const lttng::sessiond::trace::event_class& event_class) override final;
  65
  66 private:
  67         /* Coherent (parseable) fragments must be appended. */
  68         void append_metadata_fragment(const std::string& fragment) const;
  69         const lttng::sessiond::trace::type& _lookup_field_type(
  70                         const lttng::sessiond::trace::field_location& field_location) const;
  71
  72         const lttng::sessiond::trace::abi& _trace_abi;
  73         const append_metadata_fragment_function _append_metadata_fragment;
  74         details::type_overrider _sanitized_types_overrides;
  75
  76         /*
  77          * Current visit context.
  78          *
  79          * The members of a trace class hierarchy do not provide back-references
  80          * up the hierarchy (e.g. stream class to its parent trace class).
  81          *
  82          * This context allows the visitor to evaluate a "field location".
  83          *
  84          * _current_trace_class is set the first time a trace class is visited and
  85          * remains valid until the destruction of this object.
  86          *
  87          * _current_stream_class and _current_event_class are set only in the
  88          * context of the visit of a stream class and of its event class(es).
  89          */
  90         const lttng::sessiond::trace::trace_class *_current_trace_class = nullptr;
  91         const lttng::sessiond::trace::stream_class *_current_stream_class = nullptr;
  92         const lttng::sessiond::trace::event_class *_current_event_class = nullptr;
  93 };
  94
  95 } /* namespace tsdl */
  96 } /* namespace sessiond */
  97 } /* namespace lttng */
  98
  99 #endif /* LTTNG_TSDL_TRACE_CLASS_VISITOR_H */